1. Field of the Invention
The present invention relates to a semiconductor circuit, a battery cell monitoring system, a computer readable medium storing a diagnostic program, and a diagnostic method. In particular, the present invention relates to a semiconductor circuit, a battery cell monitoring system, a computer readable medium storing a diagnostic program, and a diagnostic method, employed for battery voltage monitoring.
2. Description of the Related Art
Generally a battery with plural cells (battery cells) connected together in series is employed as a battery for high output with large capacity for use in such applications as drive motors of hybrid vehicles or electric vehicles (a specific example thereof is a lithium ion battery). There are known battery cell monitoring systems for monitoring and controlling voltages of cells in such batteries.
A conventional battery cell monitoring system is configured with a battery cell group including plural battery cells, and a semiconductor circuit for measuring and controlling the voltages of the battery cells contained in the battery cell group.
In a conventional battery cell monitoring system, cell voltage equalization processing (to equalize the voltage values of each of the battery cells) and discharge control processing (to control the discharge voltage of each of the battery cells) is performed on the group of battery cells based on voltage value data of each of the battery cells obtained from a semiconductor circuit for measurement use. In such a battery cell monitoring system, due to appropriate voltage equalization processing not being performed, defects may occur.
Therefore methods for diagnosing faults relating to a discharge circuit are known. Japanese Patent Application Laid-Open (JP-A) No. 2008-175804 discloses a method for diagnosing open failure of switches employed in a discharge circuit, by detecting whether or not voltages from each end of a switch that has been switched ON state are a fixed value or less, or whether or not the voltages from each end of the switch when it has been switched OFF state are higher than a specific voltage. Further, JP-A No. 2010-95449 discloses a chopper-type comparator serving as a comparison circuit and configured with capacitors connected in parallel at the input side.
However, since the above technology requires processing in a dedicated section, such as an abnormality diagnostic section, processing time may be required and the associated power consumption may increase.